Liquid supply system

ABSTRACT

A liquid supply system that can supply liquid efficiently with reduced time needed for precooling. The liquid supply system includes a first fluid channel through which cryogenic liquid flows from an inlet 130b to an outlet 130c via a first pump chamber P1 and a second fluid channel through which cryogenic liquid flows from the inlet 130b to the outlet 130c via a second pump chamber P2. The height of the location at which the direction of the first fluid channel changes from the vertically upward direction to the vertically downward direction and the location at which the direction of the second fluid channel changes from the vertically upward direction to the vertically downward direction are the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2018/003635, filed Feb. 2, 2018 (now WO 2018/143421A1), whichclaims priority to Japanese Application No. 2017-019038, filed Feb. 3,2017. The entire disclosures of each of the above applications areincorporated herein by reference.

FIELD

The present disclosure relates to a liquid supply system used to supplycryogenic liquid.

BACKGROUND

It is known in prior art to use a liquid supply system having a pumpchamber using a bellows to cause a cryogenic liquid such as liquidnitrogen or liquid helium to circulate in a circulation fluid passage(see Patent Literature 1 in the citation list below). In such a liquidsupply system, the pump cannot operate satisfactorily if the fluidpassage that passes through the pump chamber is not filled with liquid.Hence, when the system is started for the first time or when the systemis started after maintenance, it is necessary to perform precooling soas to prevent vaporization of the cryogenic liquid in the fluid passage.To this end, before the liquid supply system is started, the cryogenicliquid is caused to flow in the fluid passage passing through the pumpchamber to precool the fluid passage.

It is known in the art to provide two bellows arranged one above theother along the vertical direction in a liquid supply system to form twopump chambers located one above the other along the vertical direction(see Patent literature 1 in the citation list below). This system candischarge cryogenic liquid from the two pump chambers alternately when ashaft member that is moved vertically upward and downward by a drivingsource moves downward and upward. In conventional liquid supply systemsof this type, the height of a location of an outlet of the liquiddischarged from the vertically upper pump chamber and the height of alocation of an outlet of the liquid discharged from the vertically lowerpump chamber are different from each other. Specifically, the latteroutlet is disposed lower than the former outlet. Hence, when thecryogenic liquid is caused to flow in the precooling process, thecryogenic liquid tends to be discharged from the latter outlet. For thisreason, it takes a long time to lower the temperature of fluid passagesin the upper region.

CITATION LIST Patent Literature

[PTL 1] WO 2016/006648

SUMMARY Technical Problem

An object of the present disclosure is to provide a liquid supply systemthat can supply liquid efficiently with reduced time needed forprecooling.

Solution to Problem

To achieve the above object, the following features are adopted.

An aspect of the present disclosure is a liquid supply system comprises:a container having an inlet and an outlet for cryogenic liquid andprovided with a pump chamber inside it; a shaft member that movesvertically upward and downward in the container; a first bellows and asecond bellows disposed one above the other along the vertical directionin the container, each of which expands and contracts with upward anddownward motion of the shaft member; a first pump chamber formed by aspace surrounding the outer circumference of the first bellows; a secondpump chamber formed by a space surrounding the outer circumference ofthe second bellows; a first fluid channel through which cryogenic liquidflows from the inlet to the outlet via the first pump chamber; and asecond fluid channel through which the cryogenic liquid flows from theinlet to the outlet via the second pump chamber, wherein a height of alocation at which the direction of the first fluid channel changes fromthe vertically upward direction to the vertically downward direction anda height of a location at which the direction of second fluid channelchanges from the vertically upward direction to the vertically downwarddirection are the same.

The liquid supply system is configured in such a way that the height ofa location at which the direction of the first fluid channel changesfrom the vertically upward direction to the vertically downwarddirection and the height of a location at which the direction of secondfluid channel changes from the vertically upward direction to thevertically downward direction are the same. Hence, when cryogenic liquidis caused to flow from the inlet to the outlet for the purpose ofprecooling, the level of the liquid flowing in the first flow passageand the level of the liquid flowing in the second fluid channel can bekept equal. This prevents situations in which liquid tends to bedischarged from one of the fluid passage and not to flow in the otherfluid passage from occurring. Therefore, the time needed for precoolingcan be shortened.

The first pump chamber may be formed by a space between a first valvethat allows the cryogenic liquid entering through the inlet to flow intothe interior of the container and a third valve that allows thecryogenic liquid to flow from the interior of the container to theoutlet, the second pump chamber may be formed by a space between asecond valve that allows the cryogenic liquid entering through the inletto flow into the interior of the container and a fourth valve thatallows the cryogenic liquid to flow from the interior of the containerto the outlet, and the third valve and the fourth valve may be disposedin upper portions of the respective pump chambers.

This arrangement enables the pump chamber to be filled with liquid up tothe height of the discharging valve. Thus, the most part of the interiorof the pump chamber is filled with the liquid. This can make the timeneeded for precooling shorter. Moreover, since the interior of the pumpchamber can be filled with liquid during precooling, gas which iscompressible fluid hardly remains in the pump chamber. Therefore, supplyof liquid by pumping can be carried out efficiently without beinginterfered with by the gas.

Advantageous Effects of the Disclosure

The present disclosure enables a reduction in the time needed forprecooling and efficient supply of liquid.

DRAWINGS

FIG. 1 a diagram illustrating the general configuration of a liquidsupply system according to an embodiment.

DETAILED DESCRIPTION

In the following, a mode for carrying out the present disclosure will bedescribed specifically on the basis of a specific embodiment withreference to the drawing. The dimensions, materials, shapes, relativearrangements, and other features of the components that will bedescribed in connection with the embodiment are not intended to limitthe technical scope of the present disclosure only to them, unlessparticularly stated.

Embodiment

A liquid supply system in an embodiment will be described with referenceto FIG. 1. The liquid supply system is suitably used for the purpose of,for example, maintaining a superconducting device in an ultra-lowtemperature state. Superconducting devices require perpetual cooling ofcomponents such as superconducting coils. Thus, a cooled deviceincluding a superconducting coil and other components is perpetuallycooled by continuous supply of a cryogenic liquid (such as liquidnitrogen or liquid helium) to the cooled device. Specifically, acirculating fluid passage passing through the cooled device is provided,and the liquid supply system is connected to the circulating fluidpassage to cause the cryogenic liquid to circulate, thereby enablingperpetual cooling of the cooled device.

<Overall Configuration of the Liquid Supply System>

FIG. 1 is a schematic diagram illustrating the overall configuration ofthe liquid supply system in the embodiment, where the overallconfiguration of the liquid supply system is illustrated in a crosssection. FIG. 1 illustrates the overall configuration in cross sectionsin planes containing the center axis, where the left side and the rightside of the center axis illustrate cross sections of different phases.More specifically, the left side of the center axis illustrates thecross sectional configuration at a location at which a first fluidchannel that passes through a first pump chamber is clearly seen, andthe right side of the center axis illustrates the cross sectionalconfiguration at a location at which a second fluid channel that passesthrough a second pump chamber is clearly seen.

The liquid supply system 10 includes a main unit of the liquid supplysystem 100 (which will be referred to as the “main system unit 100”hereinafter), a vacuum container 200 in which the main system unit 100is housed, and pipes (including an inlet pipe 310 and an outlet pipe320). The inlet pipe 310 and the outlet pipe 320 both extend into theinterior of the vacuum container 200 from outside the vacuum container200 and are connected to the main system unit 100. The interior of thevacuum container 200 is a hermetically sealed space. The interior spaceof the vacuum container 200 outside the main system unit 100, the inletpipe 310, and the outlet pipe 320 is kept in a vacuum state. Thus, thisspace provides heat insulation. The liquid supply system 10 is normallyinstalled on a horizontal surface. In the installed state, the upwarddirection of the liquid supply system 10 in FIG. 1 is the verticallyupward direction, and the downward direction in FIG. 1 is the verticallydownward direction.

The main system unit 100 includes a linear actuator 110 serving as adriving source, a shaft member 120 that is moved in vertically upwardand downward directions by the linear actuator 110, and a container 130.The linear actuator 110 is fixed on something suitable, which may be thecontainer 130 or something that is not shown in the drawings. The shaftmember 120 extends from outside the container 130 into the insidethrough an opening 130 a provided in the ceiling portion of thecontainer 130. The container 130 has an inlet 130 b and an outlet 130 cfor liquid (cryogenic liquid) in its bottom portion (vertically lowerportion). The aforementioned inlet pipe 310 is connected to the inlet130 b, and the outlet pipe 320 is connected to the outlet 130 c.

Inside the container 130 are provided a plurality of structuralcomponents that compart the interior space into plurality of spaces,which constitute a plurality of pump chambers, passages for liquid, andvacuum chambers providing heat insulation. In the following, thestructure inside the container 130 will be described in further detail.

The shaft member 120 has a main shaft portion 121 having a cavity in it,a cylindrical portion 122 surrounding the outer circumference of themain shaft portion 121, and a connecting portion 123 that connects themain shaft portion 121 and the cylindrical portion 122. The cylindricalportion 122 is provided with an upper outward flange 122 a at its upperend and a lower outward flange 122 b at its lower end.

The container 130 has a substantially cylindrical body portion 130X anda bottom plate 130Y. The body portion 130X has a first inward flange130Xa provided near its vertical center and a second inward flange 130Xbprovided on its upper portion.

Inside the body portion 130X, there are a plurality of first fluidpassages 130Xc that extend in the axial direction below the first inwardflange 130Xa and are spaced apart from one another along thecircumferential direction. Inside the body portion 130X, furthermore,there are a plurality of second fluid passages 130Xd that extend in theaxial direction above the first inward flange 130Xa and are spaced apartfrom one another along the circumferential direction. Inside the bodyportion 130X, there also is a third fluid passage 130Xe, which is anaxially extending cylindrical space provided radially outside the regionin which the first fluid passages 130Xc are provided. The bottom portionof the container 130 is provided with a fluid passage 130 d that extendscircumferentially and radially outwardly to join to the first fluidpassages 130Xc. Furthermore, the bottom plate 130Y of the container 130is provided with a fluid passage 130 e that extends circumferentiallyand radially outwardly. These fluid passages 130 d and 130 e extenduniformly along the circumferential direction to allow liquid to flowradially outwardly in all directions, namely 360 degrees about thecenter axis.

Inside the container 130, there are provided a first bellows 141 and asecond bellows 142, which expand and contract with the up and downmotion of the shaft member 120. The first bellows 141 and the secondbellows 142 are arranged one above the other along the verticaldirection. The upper end of the first bellows 141 is fixedly attached tothe upper outward flange 122 a of the cylindrical portion 122 of theshaft member 120, and the lower end of the first bellows 141 is fixedlyattached to the first inward flange 130Xa of the container 130. Theupper end of the second bellows 142 is fixedly attached to the firstinward flange 130Xa of the container 130, and the lower end of thesecond bellows 142 is fixedly attached to the lower outward flange 122 bof the cylindrical portion 122 of the shaft member 120. The spacesurrounding the outer circumference of the first bellows 141 forms afirst pump chamber P1, and the space surrounding the outer circumferenceof the second bellows 142 forms a second pump chamber P2.

Inside the container 130, there also are provided a third bellows 151and a fourth bellows 152, which expand and contract with the up and downmotion of the shaft member 120. The upper end of the third bellows 151is fixedly attached to the ceiling portion of the container 130, and thelower end of the third bellows 151 is fixedly attached to the shaftmember 120. Thus, the opening 130 a of the container 130 is closed. Theupper end of the fourth bellows 152 is fixedly attached to the secondinward flange 130Xb provided on the container 130, and the lower end ofthe fourth bellows 152 is fixedly attached to the connecting portion 123of the shaft member 120. A first space K1 is formed by the cavity in themain shaft portion 121 of the shaft member 120. A second space K2 isformed outside the third bellows 151 and inside the fourth bellows 152.A third space K3 is formed inside the first bellows 141 and the secondbellows 142. The first space K1, the second space K2, and the thirdspace K3 are in communication with each other. The space constituted bythe first to third spaces K1, K2, and K3 is hermetically sealed. Thisspace constituted by the first to third spaces K1, K2, and K3 is kept ina vacuum condition to provide heat insulation.

There are four check valves 160 including a first check valve 160A, asecond check valve 160B, a third check valve 160C, and a fourth checkvalve 160D, which are provided at different locations inside thecontainer 130. Each of these check valves 160 is an annular componentprovided coaxially with the shaft member 120. Each of the check valves160 is configured to allow flow of liquid in radial directions frominside to outside and to block flow of liquid in radial directions fromoutside to inside.

The first check valve 160A and the third check valve 160C are providedin the fluid passage passing through the first pump chamber P1. Thefirst check valve 160A and the third check valve 160C function to blockbackflow of liquid pumped by the pumping effect of the first pumpchamber P1. Specifically, the first check valve 160A is provided on theupstream side of the first pump chamber P1, and the third check valve160C is provided on the downstream side of the first pump chamber P1.More specifically, the first check valve 160A is provided in the fluidpassage 130 d provided in the bottom portion of the container 130. Thethird check valve 160C is provided in the fluid passage formed in thevicinity of the second inward flange 130Xb provided on the container130. The third check valve 160C is provided in the upper portion of thefirst pump chamber P1. The upper portion of the pump chamber refers tothe portion of the region that functions as the pump chamber that ishigher than its vertical center. In other words, the third check valve160C is provided at a position at which it allows gas in the first pumpchamber P1 to be discharged from it and allows the first pump chamber P1to be filled with liquid.

The second check valve 160B and the fourth check valve 160D are providedin the fluid passage passing through the second pump chamber P2. Thesecond check valve 160B and the fourth check valve 160D function toblock backflow of liquid pumped by the pumping effect of the second pumpchamber P2. Specifically, the second check valve 160B is provided on theupstream side of the second pump chamber P2, and the fourth check valve160D is provided on the downstream side of the second pump chamber P2.More specifically, the second check valve 160B is provided in the fluidpassage 130 e provided in the bottom plate 130Y of the container 130.The fourth check valve 160D is provided in the fluid passage thatextends from the vicinity of the first inward flange 130Xa to the secondfluid passages 130Xd. The fourth check valve 160D is provided in theupper portion of the second pump chamber P2. The upper portion of thepump chamber refers to the portion of the region that functions as thepump chamber that is higher than its vertical center. In other words,the fourth check valve 160D is provided at a position at which it allowsgas in the second pump chamber P2 to be discharged from it and allowsthe second pump chamber P2 to be filled with liquid. The exit from thesecond fluid passages 130Xd is provided at a location of the same heightas the location at which liquid flows out of the third check valve 160C.

<Description of the Overall Operation of the Liquid Supply System>

The overall operation of the liquid supply system will be described.When the shaft member 120 is lowered by the linear actuator 110, thefirst bellows 141 contracts, and the second bellows 142 expands.Consequently, the fluid pressure in the first pump chamber P1 decreases.Then, the first check valve 160A is opened, and the third check valve160C is closed. In consequence, liquid supplied from outside the liquidsupply system 10 through the inlet pipe 310 (indicated by arrow S10) istaken into the interior of the container 130 through the inlet 130 b andpasses through the first check valve 160A (indicated by arrow S11).Then, the liquid having passed through the first check valve 160A ispumped into the first pump chamber P1 through the first fluid passages130Xc in the body portion 130X of the container 130. On the other hand,the fluid pressure in the second pump chamber P2 increases. Then, thesecond check valve 160B is closed, and the fourth check valve 160D isopened. In consequence, the liquid in the second pump chamber P2 passesthrough the fourth check valve 160D (indicated by arrow T12). The liquidhaving passed through the fourth check valve 160D is pumped into thethird fluid passage 130Xe through the second fluid passages 130Xdprovided in the body portion 130X (indicated by arrow T13). Then, theliquid passes through the outlet 130 c and is brought to the outside ofthe liquid supply system 10 through the outlet pipe 320.

When the shaft member 120 is raised by the linear actuator 110, thefirst bellows 141 expands, and the second bellows 142 contracts.Consequently, the fluid pressure in the first pump chamber P1 increases.Then, the first check valve 160A is closed, and the third check valve160C is opened. In consequence, the liquid in the first pump chamber P1is pumped into the third fluid passage 130Xe provided in the bodyportion 130X through the third check valve 160C (indicated by arrowT11). Then, the liquid passes through the outlet 130 c and is brought tothe outside of the liquid supply system 10 through the outlet pipe 320.On the other hand, the fluid pressure in the second pump chamber P2decreases. Then, the second check valve 160B is opened, and the fourthcheck valve 160D is closed. In consequence, liquid supplied from outsidethe liquid supply system 10 through the inlet pipe 310 (indicated byarrow S10) is taken into the interior of the container 130 through theinlet 130 b and passes through the second check valve 160B (indicated byarrow S12). Then, the liquid having passed through the second checkvalve 160B is pumped into the second pump chamber P2.

As above, the liquid supply system 10 can cause liquid to flow from theinlet pipe 310 to the outlet pipe 320 both when the shaft member 120moves downward and when the shaft member 120 moves upward. Hence, thephenomenon called pulsation can be reduced.

The fluid passage through which the cryogenic liquid flows from theinlet 130 b to the outlet 130 c via the first pump chamber P1 will behereinafter referred to as a first fluid channel. The fluid passagethrough which the cryogenic liquid flows from the inlet 130 b to theoutlet 130 c via the second pump chamber P2 will be hereinafter referredto as a second fluid channel. As will be apparent from the abovedescription, the first fluid channel is the passage of the cryogenicliquid that enters from the inlet 130 b, then flows in the directionindicated by arrow S11, then flows in the direction indicated by arrowT11, and then flows to the outlet 130 c. The second fluid channel is thepassage of the cryogenic liquid that enters from the inlet 130 b, thenflows in the direction indicated by arrow S12, then flows in thedirections indicated by arrows T12 and T13, and then flows to the outlet130 c.

In the system, the height of the location at which the direction of theliquid flow in the first fluid channel changes from the verticallyupward direction to the downward direction (see arrow T11) and theheight of the location at which the direction of the liquid flow in thesecond fluid channel changes from the vertically upward direction to thedownward direction (see arrow T13) are the same.

The flow of liquid in the liquid supply system 10 during its operationis summarized as below. When the shaft member 120 moves downward, theliquid flows in the first fluid channel upstream of the first pumpchamber P1 but does not flow in the first fluid channel downstream ofthe first pump chamber P1. Moreover, the liquid flows in the secondfluid channel downstream of the second pump chamber P2 but does not flowin the second fluid channel upstream of the second pump chamber P2. Whenthe shaft member 120 moves upward, the liquid flows in the first fluidchannel downstream of the first pump chamber P1 but does not flow in thefirst fluid channel upstream of the first pump chamber P1. Moreover, theliquid flows in the second fluid channel upstream of the second pumpchamber P2 but does not flow in the second fluid channel downstream ofthe second pump chamber P2.

<Precooling>

Now, precooling will be described. As described in the description ofthe background art, in order to cause cryogenic liquid to circulate whenthe system is started for the first time or when the system is startedafter maintenance, it is necessary to precool the fluid passages so asto prevent the cryogenic liquid from evaporating in them. In theprecooling process, cryogenic liquid is caused to flow in theaforementioned first and second flow passages using an external drivesource. Then, the first check valve 160A, the second check valve 160B,the third check valve 160C, and the fourth check valve 16D are allopened. In consequence, the cryogenic liquid flows in the entirety ofthe first and second fluid channels including their upstream anddownstream portions at the same time.

<Advantages of the Liquid Supply System According to the Embodiment>

In the liquid supply system 10, the height of the location at which thedirection of the liquid flow in the first fluid channel changes from thevertically upward direction to the downward direction (see arrow T11)and the height of the location at which the direction of the liquid flowin the second fluid channel changes from the vertically upward directionto the downward direction (see arrow T13) are the same. When thecryogenic liquid is caused to flow from the inlet 130 b to the outlet130 c for the purpose of precooling, the level of the liquid flowing inthe first fluid channel and the level of the liquid flowing in thesecond fluid channel can be kept equal. This prevents situations inwhich liquid tends to be discharged from one of the fluid passages andnot to flow in the other fluid passage from occurring. Therefore, thetime needed for precooling can be shortened.

Others

The configuration of the first and second fluid channels is not limitedto the above-described configuration. For example, the first and secondfluid channels in the above-described system may be provided with adetour passage of liquid (i.e. cryogenic liquid) provided in the secondinward flange 130Xb of the container 130 (indicated by broken arrows T14in FIG. 1) so that the second inward flange 130Xb can also be precooledin the precooling process. This can expedite cooling of the interior ofthe system.

In the above-described configuration, the flow of liquid (i.e. cryogenicliquid) may be reversed. Specifically, the outlet 130 c may be used asan inlet, the outlet pipe 320 may be used as an inlet pipe, the inlet130 b may be used as an outlet, the inlet pipe 310 maybe used as anoutlet pipe, and the flow of liquid in the first fluid channel and thesecond fluid channel may be reversed. In the above-described embodiment,all of the fourth check valves 160 are adapted to allow flow of liquidin radial directions from inside to outside and to block flow of liquidin radial directions from outside to inside. In the case where the flowof liquid is reversed, it is necessary for all of the fourth checkvalves 160 to be adapted to allow flow of liquid in radial directionsfrom outside to inside and to block flow of liquid in radial directionsfrom inside to outside. This configuration can also provide theadvantageous effects same as the above-described embodiment.

REFERENCE SIGNS LIST

-   10: liquid supply system-   100: main system unit-   110: linear actuator-   120: shaft member-   121: main shaft portion-   122: cylindrical portion-   122 a: upper outward flange-   122 b: lower outward flange-   123: connecting portion-   130: container-   130 a: opening-   130 b: inlet-   130 c: outlet-   130 d: fluid passage-   130 e: fluid passage-   130Xa: first inward flange-   130Xb: second inward flange-   130Xc: first fluid passage-   130Xd: second fluid passage-   130Xe: third fluid passage-   130Y: bottom portion-   141: first bellows-   142: second bellows-   151: third bellows-   152: fourth bellows-   160: check valve-   160A: first check valve-   1606: second check valve-   160C: third check valve-   160D: fourth check valve-   200: vacuum container-   310: inlet pipe-   320: outlet pipe-   P1: first pump chamber-   P2: second pump chamber

1. A liquid supply system comprising: a container having an inlet and anoutlet for cryogenic liquid and provided with a pump chamber inside it;a shaft member that moves vertically upward and downward in thecontainer; a first bellows and a second bellows disposed one above theother along the vertical direction in the container, each of whichexpands and contracts with upward and downward motion of the shaftmember; a first pump chamber formed by a space surrounding the outercircumference of the first bellows; a second pump chamber formed by aspace surrounding the outer circumference of the second bellows; a firstfluid channel through which cryogenic liquid flows from the inlet to theoutlet via the first pump chamber; and a second fluid channel throughwhich the cryogenic liquid flows from the inlet to the outlet via thesecond pump chamber, wherein a height of a location at which thedirection of the first fluid channel changes from the vertically upwarddirection to the vertically downward direction and a height of alocation at which the direction of second fluid channel changes from thevertically upward direction to the vertically downward direction are thesame.
 2. A liquid supply system according to claim 1, wherein the firstpump chamber is formed by a space between a first valve that allows thecryogenic liquid entering through the inlet to flow into the interior ofthe container and a third valve that allows the cryogenic liquid to flowfrom the interior of the container to the outlet, the second pumpchamber is formed by a space between a second valve that allows thecryogenic liquid entering through the inlet to flow into the interior ofthe container and a fourth valve that allows the cryogenic liquid toflow from the interior of the container to the outlet, and the thirdvalve and the fourth valve are disposed in upper portions of therespective pump chambers.